kotatsu

kotatsu is a straightforward CLI tool aiming either at running node.js scripts or serving JavaScript/TypeScript web applications in a modern environment (modules, ES2015, Hot Module Replacement, etc.).

Its goal is to relieve developers from the really heavy stack that we now face on a daily basis when working with modern JavaScript.

The idea is to let developers new to the stack forget about it as long as they can while enabling seasoned developers to setup their environment very fast and to start customizing the stack progressively only when this is really needed.

Typical use cases for kotatsu are hot-reloaded express APIs written in ES2015, hot-reloaded React or deku applications etc. Check the use cases for a quick glance of what can be achieved.

Note that kotatsu currently uses webpack under the hood to perform its magic.

Summary

* Installation
* Usage
* Package Config
* Typescript
* Style
* JSON and YML
* Use Cases
* Interval
* Express
* Deku
* React
* Node API
* start
* serve
* monitor
* run
* build
* What on earth is a kotatsu?
* Inspiration
* License

Installation

Kotatsu can be installed globally (you should avoid this!) or within your node.js project using npm:

``bash


Within your project

npm install --save-dev kotatsu

Globally:

[sudo] npm install -g kotatsu
`

Usage

`
Usage: kotatsu {options} [entry]

Commands:
cli.js start Start a node.js script.
cli.js serve Serve a client-side application.
cli.js monitor Monitor a terminating node.js script.
cli.js run Run the given node.js script.
cli.js build Build your code for client or server.
cli.js scaffold Scaffold some typical boilerplate files.

Options:
-c, --config Optional webpack config that will be merged with kotatsu's one (useful if
you need specific loaders).
-d, --devtool Webpack devtool spec to use to compute source maps. [string]
-m, --mount-node Id of the mount node in the generated HMTL index.[string] [default: "app"]
-o, --output Output path (either directory or filename). [string]
-p, --port Port that the server should listen to. [default: 3000]
-s, --source-maps Should source maps be computed for easier debugging?
[boolean] [default: true]
--cors Should the server allow CORS? [boolean] [default: true]
--index Path to a custom HMTL index file. Will default to ./index.html if
present. [string]
--jsx Does your code uses JSX syntax? [boolean] [default: false]
--pragma JSX pragma. [string]
--sass Whether to transpile scss files (requires sass or node-sass).
[boolean] [default: false]
--typescript, --ts Whether to support TypeScript (requires typescript). Enabled by default
if target entry has .ts or .tsx extension. [boolean] [default: false]
--open Whether to open your browser on the served application.
[boolean] [default: false]
--presets Babel presets separated by a comma (example:
@babel/preset-stage-2,@babel/preset-react). [string]
--production Whether to build for production (minify + define).
[boolean] [default: false]
--progress Should it display the compilation's progress? [boolean] [default: false]
--proxy Proxy information (example: --proxy /api http://localhost:4000) [string]
--public Mounting a path to a public folder (example: --public /data ./src/data).
Can be used several times. Works with directories and single files.
[string]
-r, --html5-routing Whether to enable HTML5 routing, i.e. redirect every unknown url on the
index page to avoid reload issues. [boolean] [default: false]
--quiet Disable logs. [boolean] [default: false]
--version Show version number [boolean]
-h, --help Show help [boolean]

Examples:
kotatsu start script.js Launching the given script with HMR.
kotatsu start -c webpack.config.js script.js Using a specific webpack config.
kotatsu start --no-source-maps script.js Disabling source maps.
kotatsu start script.js -- --path test.js Passing arguments to the script.

kotatsu serve entry.js Serving the given app.
kotatsu serve --jsx entry.jsx Serving the given app with JSX code.
kotatsu serve --port 8000 entry.jsx Serving the app on a different port.
kotatsu serve --proxy /api http://localhost:4000 Proxying an API.
kotatsu serve --public /data ./src/data Serving local static files.
kotatsu serve --sass entry.js Supporting SASS stylesheets.
kotatsu serve --typescript entry.ts Serving a TypeScript app.

kotatsu build server entry.js -o ./ Build the given server script.
kotatsu build client --production entry.js -o ./ Build the given client app for production.

kotatsu scaffold index.html Dump a boilerplate html file in stdout.

`

If this is your first time using kotatsu, you should really check the use cases below to see how it could fit your workflow.

Package config

If you don't want to repeat yourself in your npm scripts know that you can use the kotatsu key of your project's package.json to keep a global configuration for the CLI:

`json
{
"scripts": {
"dev": "kotatsu serve ./entry.js"
},
"kotatsu": {
"progress": true,
"public": ["/data", "./src/data"]
}
}
`

TypeScript

kotatsu supports TypeScript out of the box. If you want to use TypeScript in your project, just ensure you have a valid tsconfig.json file and that you have installed the typescript dependencies.

If your entry does not have the .ts or .tsx extension you will need to use the --typescript flag else everything should work automatically.

Style

kotatsu lets you import CSS files out of the box. If you need to import SCSS files, you can use the --sass flag but be sure to install sass (or node-sass) for it to work.

JSON and YAML

JSON and YAML imports are automatically dealt with.

Use cases

$3

This example does not really serve a real-life purpose but merely shows you how to hot-reload a very simple node.js script.

The idea here is to create a script that will continuously print a required string into the console every 2 seconds:

1. Creating the necessary files

`js
// file: interval.js
var string = require('./string.js');

setInterval(function() {
console.log(string);
}, 2000);

// Here is the twist: whenever the string dependency is updated, we will swap it:
if (module.hot) {
module.hot.accept('./string.js', function() {
string = require('./string.js');
});
}
`

`js
// file: string.js
module.exports = 'ping';
`

2. Using kotatsu to start the script

`bash
kotatsu start interval.js
`

Now the script will start and you should see it logging ping into the console every two seconds.

Now edit the string.js file and the script will automatically update and log the new exported value of the file.

3. Let's use the same script in the browser

You would rather run this script in the browser?

`js
kotatsu serve interval.js
`

Now go to localhost:3000 and you should be able to observe the same kind of results in the console.

Remarks

This example serves another purposes: showing you that kotatsu is meant to be used on long-running scripts such as servers or UIs. If what you need is to code a terminating script, check the monitor command instead.

If you need more information about module.hot and Hot Module Replacement (HMR), go check webpack's docs on the subject.

$3

Let's setup a very simple hot-reloaded express app:

1. Installing necessary dependencies

`bash
npm i --save express
npm i --save-dev kotatsu
`

2. Creating our app

`js
// file: app.js
var express = require('express');

var app = express();

app.get('/', function(req, res) {
return res.send('Hello World!');
});

module.exports = app;
`

3. Creating our startup script

`js
// file: start.js
var app = require('./app.js'),
http = require('http');

var server = http.createServer(app);

server.listen(3000);

if (module.hot) {

// This will handle HMR and reload the server
module.hot.accept('./app.js', function() {
server.removeListener('request', app);
app = require('./app.js');
server.on('request', app);
console.log('Server reloaded!');
});
}
`

4. Using kotatsu

Launching our app with HMR so we can work comfortably.

`bash
kotatsu start ./start.js
`

You can now edit the express app live and it will automatically update without having to reload the script.

$3

1. Installing necessary dependencies

`bash
npm i --save deku
npm i --save-dev kotatsu
`

2. Creating our main component

`jsx
// file: App.jsx
import {element} from 'deku';

export default function App() {
return

;
}
`

3. Creating our application's entry

`jsx
// file: main.jsx
import {dom, element} from 'deku';
import InitalApp from './App.jsx';

const mountNode = document.getElementById('app'),
render = dom.createRenderer(mountNode);

function refresh(Component) {
render();
}
refresh(InitalApp);

// Let's handle our code's updates
if (module.hot) {
module.hot.accept('./App.jsx', function() {
const NextApp = require('./App.jsx');
refresh(NextApp);
});
}
`

4. Using kotatsu

Now let's run a server to host our app:

`bash
kotatsu serve --jsx --pragma element main.jsx
`

Note that kotatsu will serve for you a HTML index file looking quite like this:

`html












`

If you need a custom one, just use the --index argument.

Now visit localhost:3000 and you are ready to develop.

$3

React is a bit more tricky because we need to install a Babel 6 preset (react-hmre) to handle hot-loading.

1. Installing necessary dependencies

`bash
npm i --save react react-dom
npm i --save-dev kotatsu babel-preset-react babel-preset-react-hmre
`

2. Creating our main component

`jsx
// file: App.jsx
import React, {Component} from 'react';

export default class App extends Component {
render() {
return

;
}
}
`

3. Creating our application's entry

`jsx
// file: main.jsx
import React from 'react';
import {render} from 'react-dom';
import App from './App.jsx';

const mountNode = document.getElementById('app');

render(, mountNode);
`

4. Using kotatsu

Now let's run a server to host our app:

`bash
kotatsu serve --jsx ./main.jsx
`

Note that kotatsu will serve for you a HTML index file looking quite like this:

`html












`

If you need a custom one, just use the --index argument.

Now visit localhost:3000 and you are ready to develop.

Node API

`js
var kotatsu = require('kotatsu');
`

Every method of the library uses the same configuration object (similar to the CLI arguments):

required

entry string*: Path towards the entry.

optional

args array*: array of arguments to pass to the child script.
cwd string* [process.cwd()]: current working directory.
config object*: a webpack config object.
cors boolean* [true]: should the server allow CORS?
devtool string*: a webpack devtool spec.
index string*: path of the HTML index file to serve.
jsx boolean* [false]: should we handle JSX?
mountNode string* ['app']: id of the mount node in the generated HTML index file.
open boolean* [false]: Whether to open the app in you web browser as soon as served.
output string* [.kotatsu]: path of the built file.
port integer* [3000]: port that the server should listen to.
pragma string*: custom JSX pragma.
presets array*: Babel 6 presets to apply.
production boolan*: Whether to build for production, i.e. minify output and define NODE_ENV as production.
progress boolean* [false]: should the compiler display a progress bar?
proxy array*: proxy information.
quiet boolean* [false]: if true, will disable all console logs.
server function*: function called with the express app in case you want to apply custom middlewares etc.
sourceMaps boolean* [true]: should it compute source maps?

$3

`js
var watcher = kotatsu.start({
entry: 'script.js',
...
})
`

$3

`js
var server = kotatsu.serve({
entry: 'script.js',
...
})
`

$3

`js
var watcher = kotatsu.monitor({
entry: 'script.js',
...
})
`

$3

`js
kotatsu.run({
entry: 'script.js',
...
});
`

$3

`js
// side can be either 'front' or 'back'
kotatsu.build(side, {
entry: 'script.js',
...
}, callback);
``

What on earth is a kotatsu?

A kotatsu is a low Japanase table covered by a heavy blanket with an underneath heat source that keeps you warm in the cold season.

Inspiration

kotatsu is widely inspired by the following modules:

- webpack-hot-middleware by @glenjamin.
- nodemon by @remy.

License

MIT